The present invention relates to a hydraulic transmission and more particularly to a hydraulic transmission, which is infinitely differential and hydrodynamically stable.
Transmissions for automotive vehicles and certain other types of machinery require a high output torque at low rotational speeds where there may be a decline in torque requirement as output speed increases and engine load decreases. The purpose of such transmissions is to make the adjustments of speed and torque inputs and outputs to meet the load requirements. The hydraulic transmission makes these adjustments in a manner which is generally smoother than is possible in transmissions which employ clutches and mechanical shifting arrangements.
While many hydraulic transmissions in general use do make torque and speed adjustments at finite points in the range of operation of the engine and the vehicle, there are hydraulic transmissions which have the capability of producing continuously variable changes in these ratios. That is, the relationship of torque and speed input to the transmission output of torque and speed, respectively, can be continuously adjusted over a particular range of operation.
Hydraulic transmissions which are currently available and have that capability generally suffer from a variety of disadvantages. Most such systems have internal eccentric arrangements, typically with all high pressure fluid on one side and all low pressure fluid on another side with the result that there is enormous side loading on the shaft and casing, as for example in U.S. Pat. No. 2,927,430 where provision is made to bear the outward thrust of the driven rotor. In such a case, transmission construction requires the use of large and heavy components with consequent increase in cost, loss of efficiency, and greater need for space to accommodate the transmission.
In view of the long term trend to reduce the size and weight of automotive vehicles to improve fuel efficiency and stretch out available and potential supplies of hydrocarbon fuels, it is readily seen that any significant improvement in transmission design which will make it possible to reduce the size and weight of this essential component of automotive vehicles using internal combustion engines is likely to have a very beneficial effect on this form of transportation.
In addition, smaller and lighter weight transmissions will tend to reduce the cost of such vehicles and any other machinery requiring transmissions of the type herein described.